improved rat config: ignore only expected IT results

git-svn-id: https://svn.apache.org/repos/asf/maven/shared/trunk@1595965 13f79535-47bb-0310-9956-ffa450edef68
code simplification

git-svn-id: https://svn.apache.org/repos/asf/maven/shared/trunk@1595974 13f79535-47bb-0310-9956-ffa450edef68
avoid Invoker instantiation: define static methods

git-svn-id: https://svn.apache.org/repos/asf/maven/shared/trunk@1595975 13f79535-47bb-0310-9956-ffa450edef68
use Set instead of Map since the Map value is unused

git-svn-id: https://svn.apache.org/repos/asf/maven/shared/trunk@1595985 13f79535-47bb-0310-9956-ffa450edef68